The central idea of our project is that understanding intra-membrane protein-protein interactions, and finding specific agents for their disruption may define a novel strategy for combatting enveloped virus infections. Our objective is to characterize, understand, and predict the structural interactions that occur in the transbilayer region when membrane proteins oligomerize. Our findings in two membrane protein systems (bacteriorhodopsin (BR) and glycophorin A (GpA)) show that such interactions can be important factors in driving oligomerization and can have a high degree of specificity. Preliminary results suggest that the transbilayer regions of HIV gp41 and influenza hemagglutinin (HA) are also capable of oligomerization without their respective endo- and ecto-domains. If either the oligomerization or the function of viral envelope proteins is mediated to some extent by association of their transmembrane domains, then disruption of these interactions by pharmacological agents may prove useful. We will use mutagenesis, disruptive agents, thermal denaturation and variations in the lipid environment to define interactions driving oligomerization in gp41 and HA transbilayer domains. We will then express the altered whole protein in cultured cells to explore the effect of disruptive mutations on oligomerization and fusion activity. Structures of the transmembrane portions will be explored using NMR and other spectroscopic methods, and thermal disruption will be used to probe interaction energies. Computational modeling will be exploited to lead toward generalization of ideas, with the aims of predicting structure and serving as a basis for drug design enhancement. Finally, we hope to exploit our assays in high capacity screens to find agents specific for disruption of transmembrane interactions.